The present invention relates, in general, to methods for scrubbing surfaces of field emission displays, and, more particularly, to methods for scrubbing anode plates of high voltage field emission displays.
Field emission displays (FED""s) are known in the art. High voltage FED""s are operated at anode voltages that are greater than about 1000 volts. A typical high voltage anode plate includes a transparent substrate upon which is formed an anode, which typically is made from indium tin oxide. Cathodoluminescent phosphors are disposed on the anode. It is also known to provide an aluminum layer on the cathodoluminescent phosphors in order to improve brightness. The aluminum layer improves the brightness of the display image by reflecting toward the viewer light that is initially directed away from the viewer. Because of the high voltage operation, incident electrons are able to traverse the aluminum layer to activate the cathodoluminescent phosphors.
However, aluminum oxide (Al2O3), which is known to exist at the outer surface of the aluminum layer, readily forms hydrates. The water from the hydrates can be liberated into the vacuum of the FED when the aluminum layer is struck by the emission current. Furthermore, it is known that aluminum oxide can be decomposed by electron bombardment, thereby evolving oxygen into the vacuum of the FED. It is known that the presence of water and oxygen are undesirable because they can react with the electron emitter structures, thereby contaminating them and causing deterioration of their emissive properties.
It is known in the vacuum industry to clean and passivate surfaces of vacuum devices using two distinct steps. The first step consists of scrubbing the contaminated surface with a scrubbing agent, such as an electron beam, an ion beam, or ultraviolet light. The second step consists of subsequently depositing a carbon layer on the scrubbed surface. The carbon layer is known to act as a passivation layer. However, this multi-step prior art scheme is time consuming and requires distinct process equipment and/or different materials for each step.
Accordingly, there exists a need for a method for scrubbing an anode plate of a field emission display, which overcomes at least these shortcomings of the prior art.